1. Field of the Invention
The present invention relates to a measuring-instrument remote-calibration system and a measuring-instrument remote-calibration method.
2. Description of the Related Art
Generally, a system that supplies measuring standards to measuring instruments is called a “traceability system.” In such a system of the related art, as shown in FIG. 5, the measuring standards are supplied in a “by-bringing” technique, which utilizes a so-called “hierarchy,” in which a measuring standard having a lower accuracy 902 is brought to 905, and calibrated against, a measuring standard having a higher accuracy 901.
This technique is disclosed in, for example, “Denshi Keisoku (Electronic Measurement) (Kaitei-ban (Revised Edition))” written by Yasuo TSUZUKI, edited by the Institute of Electronics, Information and Communication Engineers (a Japanese incorporated body), and published by Corona Publishing Co., Ltd on Jan. 30, 2001 (see pages 23 and 24, FIG. 2.4 “Torehsabirithi Taikei (Traceability System)”).
A calibration certificate 907 may then be issued from an authority having the higher standard 901 to an authority having the lower standard 902.
Generally, the “by-bringing” standard technique incorporates several layers of authorities, with the highest calibration authority being the respective national institute of metrology (or an equivalent body).
In Japan, such a measuring standard supply system is controlled by the Japan Calibration Service System (JCSS), and the highest calibration authority is the National Metrology Institute of Japan (NMIJ) in the National institute of Advanced Industrial Science and Technology. In the United States, the National Institute of Standards and Technology (NIST) is the highest calibration authority.
NIST currently is implementing a remote calibration research project called “SIMnet” (“SIM” means the Interamerican Metrology System and “net” represents calibration by using the Internet). In SIMnet, at the present stage, digital voltmeters capable of measuring electrical properties such as direct-current voltage, current, and resistance are calibrated by NIST and provided to various Central and South American countries that have no advanced national standard authorities. The digital voltmeters are then utilized to compare low level standards in those countries with the calibrated values and report any differences using the Internet.
However, exchanging calibrated results with the Central and South American countries is problematic. For example, problems result from the tightness of NIST's Internet security (e.g., firewalls), which is enforced to prevent cyberterrorism on information communication networks. Further, this system merely indicates the differences between the calibrated standards and the local standards, and thus cannot provide highly accurate measuring standards, such as those utilized in the “by-bringing” method discussed above, to the foreign countries remotely.
In fact, the present standard-supplying systems suffer from many disadvantages. Specifically, the hierarchical structure of the standard-supplying system is so strict that the system has difficulty in coping with a rapid social change. Also, due to the hierarchical structure, the lower layer has a respectively higher uncertainty. Additionally, the time required for calibration, that is, a time between acceptance of an instrument to be calibrated and issuance of a calibration certificate, is long. Further, because the standard-supplying system uses a so-called “by-bringing” standard supplying technique, a calibrated value is guaranteed only within a defined area and time of calibration. Accordingly, it is impossible to provide a calibration service to a non-local entity, such as a manufacturing plant of a domestic company that is located overseas.